Randall L. Halcomb, director of medicinal chemistry at Gilead Sciences in Foster City, Calif., revealed the structure of GS-9620, a potential drug for chronic hepatitis B as well as hepatitis C. The molecule is an orally administered agonist of Toll-like receptor 7 (TLR7), a receptor on immune cells that responds to virusderived RNA. Gilead’s scientists had a specific reason for targeting the immune system, Halcomb told C&EN. “In general when a hepatitis B patient goes . . .